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Image Reconstruction with a Fast, Monolithic Proton Radiography System

D DeJongh1*, E DeJongh2 , V Rykalin3 , J Welsh4 , M Pankuch5 , N Karonis6 , C Ordonez7 , K Duffin8 , J Winans9 , G Coutrakon10 , C Sarosiek11 , (1) ProtonVDA Inc, Batavia, IL, (2) ProtonVDA, Naperville, IL, (3) ProtonVDA, Naperville, IL, (4) Chicago Association for Research and Education in Science, Hines, IL,(5) Northwestern Medicine Chicago Proton Center, Warrenville, IL, (6) Northern Illinois University, Dekalb, IL, (7) Northern Illinois University, Dekalb, IL, (8) Northern Illinois University, Dekalb, Illinois, (9) Northern Illinois University, Dekalb, IL, (10) Northern Illinois University, Dekalb, IL, (11) Northern Illinois University, Dekalb, IL


(Sunday, 7/29/2018) 3:00 PM - 6:00 PM

Room: Exhibit Hall

Purpose: Proton radiography enables proton range verification in addition to the anatomical alignment verification currently obtained with x-ray radiography. Design specifications require that a clinical system be simple, lightweight, easily scaled to large field sizes, operate at high speed to maximize patient throughput, and expose the patient to the minimum possible radiation dose for a given resolution. We are developing a system to produce images of proton stopping power by tracking individual protons before and after the patient and measuring the proton residual range after traversing the patient. Due to multiple scattering effects, each proton deviates randomly from its projected trajectory. To achieve optimal spatial resolution, an image reconstruction algorithm must fully exploit the individual three-dimensional proton position information.

Methods: We have developed an iterative algorithm for radiography fully exploiting proton path information to produce projective radiographs with reduced blurring from multiple scattering. Simulations of our detector, with and without multiple scattering effects included, determine the expected accuracy of our proton path reconstruction, and the impact on the resolution of the reconstructed image.

Results: Reconstruction of simulated images with the iterative algorithm shows spatial resolution of typically 1 mm compared to the 4 mm obtained by simply binning protons into pixels. Our system has passed integration tests and is undergoing calibration, which will enable comparison of actual and simulated images.

Conclusion: A proton radiography system optimizing image sharpness and dose (~0.005 cGy) to the patient will individually track protons before and after the patient. An iterative algorithm produces images with spatial resolution given by the tracking accuracy. Our fully functional system, in development, will include the use of GPU processors for rapid reconstruction of the radiograph.

Funding Support, Disclosures, and Conflict of Interest: Funded by NCI grant R44CA203499. Presenting author is a co-owner of ProtonVDA Inc which holds intellectual property rights on certain proton imaging innovations.


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